The present invention relates to a magnetic head of magnetoresistance effect type to be used for a magnetic disk drive and a process for production thereof. More-particularly, the present invention relates to a magnetic head of magnetoresistance effect type which includes a magnetoresistive element and an overvoltage protective circuit arranged together on a slider, and to a process for production thereof.
A magnetic disk drive is usually provided with a magnetic head of magnetoresistance effect type which is a magnetoresistive element (such as MR element, MGR element, and TMR element). Unfortunately, the magnetoresistive element is easily broken on account of its low withstand voltage. Existing GMR (Giant Magnetoresistive) heads are broken at about 0.5 V and promising TMR (Tunneling Magnetoresistive) heads are broken at about 0.3 V. In other words, TMR heads are subject to electro-static destruction (ESD) resulting from static electricity (hundreds of mV) which occurs during fabrication or within the magnetic disk drive.
A usual measure to cope with this situation is to connect a diode clamp circuit to the input of the preamplifier of the MR element. This diode clamp circuit prevents a voltage higher than 0.6 V from being applied across both terminals of the MR element or across the MR element and the ground after the wired components have been incorporated into the head stack assembly (HSA). The 0.6 V is the voltage drop (Vf) that occurs in the forward direction of the diode.
Japanese Patent Laid-open No. 2002-358608 (pp. 4-5, FIG. 1) discloses a technology relating to protection from overvoltage. This technology is designed to protect the magnetic head from disturbing noise which might come in during fabrication, while keeping both high recording density and high response speed. The object is achieved in the following manner. A silicon layer held between insulating films is formed on the substrate. On this silicon layer are formed at least one diode clamp circuit and a recording-reading amplifier circuit. The clamp circuit electrically connects any two members selected from the first shield, the second shield, the first electrode, and the second electrode with each other, all of which constitute the magnetoresistive element, and the substrate.